行政院國家科學委員會專題研究計畫成果報告:下肢肌力強化訓練運動劑量最佳化之研究

行政院國家科學委員會專題研究計畫 成果報告

下肢肌力強化訓練運動劑量最佳化之研究

中 華 民 國 94 年 10 月 18 日

ABSTRACT

Background and Purpose. One repetition maximum (1RM) for leg press is used to

be a clinical reference for resistance training of lower extremities. However, the

Western standard was built on “bilateral”leg press test from “full”hip and knee joint

flexion to extension regardless of race and clinical application. Subjects and

Methods. Two hundred and twenty healthy sedentary volunteers(105 males and 115

females) aged 20-80 years old and 17< BMI< 31 performed as many repetitions of

unilateral leg press from 90°knee flexion to extension as possible. Results. 1RM

strength for leg press was correlated with body weight, age and gender (p<.05 ). The

regression equation was: unilateral 1RM= 8.6+ 1.0 x BW (kg)- 8.3 x Age (1-3,

representing 20-39, 40-59, 60-80 y/o, respectively) + 10.2 x Gender (female=1,

male=2), R2=0.74 .Discussion and Conclusion. The ability to perform leg press

increases with weight, decreases with increasing age, and females do not perform as

well as males. The present study provides a more realistically reference for clinical

applications.

INTRODUCTION

Resistance training has been shown to be one of the most effective methods for

strength training of lower extremities. It can not only promote the strength of lower

extremities, but also improve the functional performance of jumping and running in

the youth. In addition, it could help the elderly to maintain or increase

cardiopulmonary fitness, prevent cardiovascular disease, improve muscle strength,

maintain joint flexibility and walking balance, prevent falls, decrease anxiety,

depression, and promote their social activities, as well as quality of life.

One repetition maximum (1RM) for leg press is used to be a clinical reference for

resistance training of lower extremities. According to the past research report, it was

proved that the 1RM of male or female was related to their weight. However, the

Western standard was built on bilateral leg press test from full hip and knee joint

flexion to extension. It is hard for therapists to apply it to clinic directly, because the

body figures, life styles, and exercise habits of people in Taiwan differ from

Easterners. And bilateral leg press is not suit for unilateral injured case, because

therapists can not know how much effort the affected side does make, and can not

control the appropriate training dosage also. Furthermore, leg press from full hip and

patellofemoral pain syndrome, because the joint stress increases gradually with

increasing knee flexion angles in closed kinetic chain exercise. And it is also hard for

elderly people to make effort in such a situation that full flex the hip and knee joints.

In order to approach a more realistically assessment of leg-press 1RM strength for

further clinical uses, the purpose of the present study was to investigate unilateral

1RM strength for leg press from 90° knee flexion to extension in different genders

METHODS

Participants

Healthy participants aged 20 to 80 years old without lower limb lesions or injuries

involving hip, knee, or ankle joints, and free of low back pain and cardiopulmonary

diseases were recruited from Taipei city, Taiwan using advertisement. The exclusion

criteria were inability to walk continuously more than 30 minutes without joint pain,

or preservation of less than 70% range of motion of hip, knee, or ankle joint, or being

engaged in some regular exercise (defined as physical activity at least three times per

week, and exercise of more than 15 min after warm-up exercise), or BMI≧31,≦17.

The reason to exclude people with regular exercise habits and abnormal BMI are that

only 20.5% people in Taiwan exercise regularly and people with abnormal body

figures are relatively smaller population than usual ones. Thus we think they can not

present mostly healthy people in Taiwan.

All participants were volunteered to participate in this study. Initially 240 healthy

participants (113 males and 127 females) were recruited. Subsequent exclusion were

based on an inability to walk continuously more than 30 minutes without joint pain

(n=4), presence of regular exercise habits (n=11), and BMI≧31 or ≦17(n=5).

All participants aged 20 to 80 years old were initially recruited from 6 decades. Since

no statistical differences of leg-press 1RM strength were found between these

adjacent decades (p>.05), all participants were than re-grouped into 3 groups: 20-39,

40-59 and 60-80 for further statistical analyses.

Measurement of 1RM strength for leg press

We used EN-Dynamic Track leg press machine for 1RM strength measurement. The

initial testing position was sitting with 90°knee flexion with foot on force plate and

hands on the seat’s handles. We defined leg press movement as forward and backward

movement, indicating knee flexion to full extension, than back to initial position. The

dominant limb and non-dominant limb were tested by climbing stairs then tested for

1RM in a random order. The initial resistance setting depended on the gender and age

of the participants. For male participant, the resistance was set at 1.0, 0.8, 0.6 times of

their body weight, and 0.9, 0.7, 0.5 times of body weight for female participants. All

participants were encouraged to do their best to repeat unilateral leg press

continuously with the first second and the following second pressing the leg forward

and backward until they could press no more ones or failed to complete a full range of

motions again, thus the test discontinued. In addition, during the test the therapists

knees during extension. Finally, the resistance loadings and repetition times of each

participant were recorded for 1RM calculation using Holten Diagram.

To assess the intra-rater reliability of these measurement protocols, 16 participants

were repeatedly measured 3 to 5 days apart. The ICC value was 0.98, suggesting a

high intra-rater reliability of 1RM strength for leg press test.

Statistical Analyses

SPSS 11.0 software was used for the statistical analyses. Descriptive statistics were

used to depict the subjects’characteristics, such as age, body height, and body weight.

3x2 two-way independent ANOVA was used to compare gender and age differences

in 1RM strength. The significant level was set at α=.05. If any significance was

found post hoc comparisons were further tested with Bonferroni adjustment. The

stepwise regression was then performed to analyze the association of 1RM strength

with gender, age, body height (BH), body weight (BW), body mass index (BMI), and

RESULTS

Table 1 presents the demographic information of the healthy participants. Among all

participants 96.8% were right-leg dominant. The normalized 1RM strength for leg

press was presented as 1RM/BW of dominant or non-dominant limb for further

comparison between participants. There was no significance between limbs (p>.05),

and the unilateral 1RM strength for leg press in different genders and age groups were

shown in Table 2. Female participants’unilateral 1RM strength were about 1.2, 1.1,

and 1.0 times of their body weight for 20-39, 40-59, and 60-80 age groups while male

participants’were about 1.3, 1.2, and 1.1 times of body weight.

---Insert Table 1 and Table 2 about

here---Figure 1 and here---Figure 2 present the gender and age differences in unilateral 1RM

strength for leg press. Female participants’1RM strength were always less than those

of male participants despite the age (all p<.05 ). And 1RM strength decreased with

increasing age in both female and male groups (all p<.05 ).

here---The means and standard deviations (SD) of unilateral 1RM strength for leg press were

then used for grading strength value into 5 grades: excellent, good, average, fair, and

poor. We defined average grade as mean value plus or minus a SD (mean±SD), good

and fair grade as mean value plus or minus 1 SD to 2 SD, excellent and poor grade as

above or below mean value plus or minus 2 SD, shown in Table 3.

---Insert Table 3 about

here---Stepwise regression analysis showed that unilateral 1RM strength for leg press was

correlated with body weight, age and gender (p<.05 ). The regression equation was:

unilateral 1RM= 8.6+ 1.0 x BW (kg)- 8.3 x Age (1-3, representing 20-39, 40-59,

DISCUSSION

The present study reveals the performance of unilateral leg press from 90° knee

flexion to extension in healthy adults. We recognize the unilateral 1RM strength for

leg press in different genders and age groups. These values provide therapists some

information while comprising with clinical patients or frail elderly.

Our finding that there was no significance between dominant and non-dominant limbs

in 1RM strength for leg press was consistent with previous studies that had reported

no differences between torque, maximal power and endurance generated by left and

right knee extensors and flexors. Although the previous studies used the isokinetic

machines and tested only a single muscle group of lower extremities that differed

from our study that measured the closed kinetic chain performance of multiple muscle

groups of lower extremities that was more closely to our life style, we got the same

results that the dominant limb tended to be better than the non-dominant limb in

functional use, but not in exertion performance for a short time.

In general, muscle strength differs in men and women, and weakens with increasing

age due to different muscle structure and function. The present study results supported

between adjacent decades that the same as another study that tested the strength of the

ankle plantar flexors using manual muscle test. There were two common sides of

these two tests, first we both tested the anti-gravity muscle groups of lower

extremities, and second both studies gave their participants a constant load to test the

repetition times as the results to calculate strength performances, thus the outcomes

are reasonable and acceptable .

The present study first used the unilateral leg press test from 90° knee flexion to

extension to test the 1RM performance because the practical concerns in clinic. Due

to the effects of unilateral limb performance, different joint position angle, race and

culture, we could not compare our study results with the reported values of other

studies directly. However we build a new reference for Easterners. We can estimate

one’s leg 1RM strength by regression equation and grading of his or her strength for

further comparison with people in the same age group and with the same gender.

When generating the results to populations, there is a caution that they might meet

some criteria such as sedentary lift style and normal body figures (17< BMI< 31), this

is also the area where we can make further efforts to establish the normative data for

CONCLUSION

“Unilateral”1RM strength for leg press “from 90° knee flexion to extension”provide

clinicians to view the 1RM performance of lower extremities more practically.

Leg-press 1RM strength was varied with body weight, age and gender. The ability to

perform leg press increases with weight, decreases with increasing age, and females

do not perform as well as males. The present study provides a more realistically

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Table 1.

Demographic Data of Study Participants (mean±SD )

Subjects N Age (yr) Body height (cm) Body weight (kg) 20-39y/o Male Female 38 39 27.9±5.2 26.4±4.2 171.6±5.4 160.4±5.9 69.0±10.0 52.8±7.5 40-59y/o Male Female 35 39 50.6±6.1 52.7±4.4 171.2±4.7 156.1±3.9 72.7±8.9 56.6±6.8 60-80y/o Male Female 32 37 68.2±5.0 66.8±5.0 165.0±5.9 155.1±4.6 65.5±9.1 56.8±5.4 Total Male Female 105 115 47.8±17.4 48.3±17.4 169.4±6.1 157.2±5.4 69.1±9.7 55.4±6.8

Table 2.

Unilateral Leg-Press 1RM /BW in Males and Females among Three Age Groups

Male (mean±SD) Female (mean±SD) 20-39y/o 1.37±0.12 1.20±0.17 40-59y/o 1.22±0.14 1.11±0.18 60-80y/o 1.08±0.17 0.97±0.19

Table 3.

Grades of Unilateral Leg-Press 1RM /BW in Males and Females among Three Age Groups

Male Female

20-39y/o 40-59y/o 60-80y/o 20-39y/o 40-59y/o 60-80y/o

Excellent >1.61 >1.50 >1.42 >1.54 >1.47 >1.35

Good 1.50-1.61 1.37-1.50 1.26-1.42 1.38-1.54 1.30-1.47 1.17-1.35

Average 1.25-1.49 1.08-1.36 0.91-1.25 1.03-1.37 0.93-1.29 0.78-1.16

Fair 1.13-1.24 0.94-1.07 0.74-0.90 0.86-1.02 0.75-0.92 0.59-0.77

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 20-39 40-59 60-80 Age group U n il a te r a l L e g -p r e ss 1 R M /B W Male Female Figure 1.

Gender Differences in Unilateral Leg-Press 1RM /BW among Three Age Groups

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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Male Female U n il a te r a l L e g -P r e ss 1 R M /B W 20-39y/o 40-59y/o 60-80y/o Figure 2.

Age Differences in Unilateral Leg-Press 1RM /BW among Male and Female Participants

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